1. Field of the Invention
The present invention provides a downhole adjustable bent housing for use in directional drilling of wells used to recover oil and gas, and a method for directionally drilling a well to recover oil and gas.
2. Background of the Related Art
Wells are generally drilled to recover natural deposits of hydrocarbons and other desirable, naturally occurring materials trapped in geological formations in the earth""s crust. A slender well is drilled into the ground and directed to the targeted geological location from a drilling rig at the surface. In conventional xe2x80x9crotary drillingxe2x80x9d operations, the drilling rig rotates a drillstring comprised of tubular joints of drill pipe connected together to turn a bottom hole assembly (BHA) and a drill bit that are connected to the lower end of the drillstring. The BHA typically comprises a number of downhole tools including adjustable bent housings, drill collars and mud motors, and is generally within 30 feet of the drill bit at the end of the drillstring. During drilling operations, a drilling fluid, commonly referred to as drilling mud, is pumped down the interior of the drillpipe, through the BHA and the drill bit, and back to the surface in the annulus around the drillpipe. Mud motors are often used to rotate the drill bit without rotation of the drillstring. Pressurized mud pumped down the interior of the drillstring is used to power the mud motor that is mechanically coupled to and turns the nearby drill bit. Mud motors offer increased flexibility for directional drilling because they can be used with stabilizers or bent subs which impart an angular deviation to the BHA in order to deviate the well from its previous path and in the desired direction.
Surface adjustable bent housings are downhole tools that make up part of the BHA and are typically connected either between the mud motor and the drill bit or above the mud motor and the drill bit. Such bent housings are designed to provide an angular deviation in the BHA to directionally orient drilling action at the drill bit. A surface adjustable bent housing may be adjusted to a particular setting by tripping the drillstring and setting the bent housing to impart a desired angular deviation to the well.
A downhole adjustable bent housing offers savings in rig time and well costs because it is adjustable without being removed from the well. A downhole adjustable bent housing that is positionable, or deployable, from the surface can be used to efficiently influence the drop or build angle of the boring direction of the drill bit. The angle of attack of the drill bit and the resulting direction of the well can be guided using the downhole adjustable bent housing.
It is well known in the drilling industry how to obtain reliable three-dimensional location data for the bottom of the well being drilled. The driller compares this information with the target bottom hole location to determine needed adjustments in the path of the well, and the adjustments to the direction of drilling of the well may be made using the present invention.
Prior art surface adjustable bent housings use a complicated series of three connected housings that rotate independently to provide varying configurations from aligned to bent relative to the BHA. These tools require complex schemes for controlling rotational positions of each housing.
It is therefore an object of the present invention to provide a downhole adjustable bent housing that can be easily and repeatedly deployed or retracted by controllable changes made at the surface in hydraulic mud pressure in the drillstring.
It is a further object of the present invention to provide a downhole adjustable bent housing that can be adjusted without the use of wired or cabled control systems that complicate drilling operations, and that is reliable and simple to deploy and retract.
It is a further object of the present invention to provide a downhole adjustable bent housing that, once locked into its deployed position, allows the driller freedom to change the rate of the mud pumps without affecting the deployed condition of the tool.
It is a further object of the present invention to provide a downhole adjustable bent housing that provides the driller with reliable detection of the deployed or retracted status of the tool.
The above-described objects of the present invention, as well as other objects and advantages, are achieved by a downhole adjustable bent housing that is deployed and retracted by the driller by using the mud pumps located at the surface and used to circulate drilling mud in the well during the drilling process. The present invention does not require wires, cables or cumbersome reciprocation of the entire drillstring to deploy, lock or re-align the downhole adjustable bent housing, and the downhole adjustable bent housing is controllably deployed and realigned without a trip using hydraulic pressure provided by the mud pumps. The present invention provides the driller with readily available information regarding the status of the tool (aligned or deployed, and to what extent), utilizes existing mud pumps as its source of control, and is compatible with existing mud motors and other downhole equipment. The present invention provides reliable deployment and re-alignment of the downhole adjustable bent housing without interfering, with the mechanical transfer of transmission shaft power from a mud motor connected above the tool to a drill bit connected below the tool.
The present invention provides a surface-operated downhole adjustable bent housing with a bendable housing and a hydraulically actuated, tubular mandrel that engages and displaces an articulating member which, when actuated by the mandrel, sets or deploys the downhole adjustable bent housing, into its bent, or non-aligned configuration. The downhole adjustable bent housing comprises a mandrel housing 33 and a member housing 34 joined at a knuckle or joint to form a bendable housing. The housings and the knuckle provide a common center passage accommodating a transmission shaft providing power from the mud motor to the drill bit, and provide substantial rigidity to the bendable housing structure in its inactive and deployed configurations. Under the bending force provided by mechanical interaction of the mandrel and the articulating member, the joined sections of the housing are made to angularly deviate one relative to the other to form a slight angle in the downhole adjustable bent housing.
The mandrel is reciprocally disposed within a mandrel housing, but protrudes through an opening in the knuckle and into a passage in the articulating member pivotally secured in the member housing. When actuated, the mandrel overcomes a return spring that biases the mandrel towards its inactive position. The mandrel is hydraulically actuated to cycle through a number of predetermined positions to allow drilling with the downhole adjustable bent housing in either the deployed (bent) or inactive (aligned) configurations. For example, the mandrel can be hydraulically actuated from its inactive position (spring force exceeds the mud pressure forces on the mandrel) to an intermediate position (mandrel displaced into contact with the passage of articulating member, but no deployment of the downhole adjustable bent housing), back to the inactive position, and later to its deployed position (mandrel displaced further to enter the passage in the articulating member to deploy the bent housing).
The mandrel is actuated towards the articulating member by exposing the mandrel to at least a threshold drilling mud pressure applied through the drillstring by the mud pumps at the surface. When the drilling mud pressure overcomes the opposing return spring force, the mandrel is displaced to the extent allowed by the rotational position of the control collar as it engages a guide finger that is fixed to the housing. The mandrel is locked into its displaced position by the force of the mud pressure on the mandrel until the pressure is reduced below the threshold pressure. The mandrel is said to be xe2x80x9clockedxe2x80x9d into its intermediate (or deployed) position(s) only in the sense that the mandrel is hydraulically secured into its intermediate (or its deployed) position until the mud pressure drops below the threshold pressure and mud forces on the mandrel are overcome by the force of the return spring.
With a first actuation, the mandrel is displaced to its intermediate position by mud pressure axially displacing the mandrel and an attached rotating position control collar, such as a xe2x80x9cJ-slotxe2x80x9d collar. The reciprocation of the mandrel is controlled by interaction of the control collar and the housing. The leading end, or nose, of the mandrel enters the receiving port of the articulating member and engages the passage therein without rotation of the articulating member or laterally displacing the articulating member. In this intermediate position, the contact between the nose of the mandrel and the articulating member provides additional rigidity to the downhole adjustable bent housing while drilling in a path defined by the tool in its undeployed configuration. The mandrel is unlocked from its intermediate position by reducing the pressure in the drillstring to below the threshold pressure and allowing the force of the return spring to stroke the mandrel back to its original, inactive position.
With a second actuation, the mandrel is displaced beyond its intermediate position to its deployed position. Again, the extent of travel of the mandrel is determined by the control collar, but the control collar has a different angular orientation relative to the housing. The controlled angular orientation of the control collar is provided by a series of interconnected grooves in the collar that interface with the guide finger, and the grooves allow further displacement of the mandrel to its deployed position on the second actuation. When actuated to its deployed position, the nose of the mandrel engages and forcibly aligns the passage in the articulating member with the shaft of the mandrel. The articulating member rotates to receive the shaft within the passage and is laterally displaced from its inactive position to its deployed position.
The downhole adjustable bent housing is biased towards its inactive (aligned) position by the knuckle or other biasing components that generally urge the mandrel housing and the member housing into axial alignment. More particularly, the space between the mandrel housing and the member housing is beveled on the tool face side to bias the two into axial alignment when the drill string is rotated. Also, beveled lock rings act to prevent bending once a straight position is achieved. The passage in the articulating member is not axially aligned with the mandrel when the downhole adjustable bent housing is in its inactive, aligned configuration. The passage in the articulating member is adapted at its receiving port to receive the nose of the mandrel upon deployment of the downhole adjustable bent housing. The nose of the mandrel and the receiving port of the articulating member are tapered or contoured to rotate the articulating member to generally align the passage for further receiving of the mandrel, thereby directing the end of the mandrel towards the passage. As the mandrel is forced into its deployed position within the passage of the articulating member, a misalignment between the shaft of the mandrel and the wall of the passage causes sliding interference between the mandrel and the articulating member as the mandrel moves to its deployed position. The sliding interference results in a lateral force on the articulating member as the mandrel thrusts into the passage. The forced alignment of the previously axially misaligned passage of the articulating member provides a lateral bending force that is transferred to the member housing through supports pivotally securing the articulating member within the member housing. The transfer of force to the member housing overcomes the biasing alignment of the knuckle or other components tending to align the mandrel housing and the member housing, thereby bending the downhole adjustable bent housing and deploying the tool.
The articulating member may be pivotally disposed within the member housing using axle ears located on opposite lateral sides of the articulating member. These axle ears are generally aligned one with the other, and may be pivotally received within recesses on the inside wall of the member housing. The lateral force imparted to the articulating member by the mandrel as it is received into the passage is transferred through the axle ears to the member housing. The lateral force imparted to the member housing causes the downhole adjustable bent housing to bend at the knuckle so that the member housing, and the connected drill bit, are out of alignment with the mandrel housing. This deployed configuration of the downhole adjustable bent housing is used for imparting a curve, or angular deviation, to the well being drilled. As drilling on a curved path progresses with the tool in the deployed configuration, the articulating member and the mandrel remain locked in their deployed position by the force of the drilling mud pressure bearing on the mandrel until the drilling mud pressure is reduced below the threshold pressure. After the mandrel is unlocked from its deployed position, the force of the return spring causes the mandrel to withdraw from the passage and move towards its inactive position. The control collar rotates during each induced angular rotation of the collar to cycle the downhole adjustable bent housing through the inactive, intermediate and deployed positions as needed to deviate the well in the desired path. It should be recognized that other and further actuation cycles can be envisaged, such as a cycles adding a third actuated position achieving partial deployment of the downhole adjustable bent housing.